I'm writing a Masters Thesis and am just not sure if every source I've cited in my thesis, I need to disuss in the Literature Review?
While you have to cite every source that you reference properly, you defenitely don't have to discuss every source in the literature review. Some sources you cite might only be needed for little things like an equation, a standard used for testing, or a confirmation of an hypothesis you make, market projections, single statistical results, etc. Other sources might be slightly off-topic but still relevant for a small part of the thesis.
Limit the sources discussed in the literature review to those that fit there.